The Yato 3-20 mm Step Drill Bit Set (3 Pcs) is a perfect tool for woodworkers and DIYers. It features a high-grade steel shank, which allows you to use it in high-speed, high-torque applications. The step bit is ideal for drilling larger holes with ease and is great for woodworkers who need extra help with drilling through different types of material. Each bit features a smooth cutting edge that makes it easy to use on soft materials like wood, plastic and even metal. The drill bits are made from high-quality steel that is CNC machined for a precise fit every time. This ensures that the bits stay sharp longer so you don't have to stop what you're doing just because your drill bit has dulled out after only one use. HSS 4241 is a high-speed steel, an alloy of chromium, molybdenum and tungsten. It has better wear resistance and strength than the standard HSS (high speed steel). The use of this steel makes the drill bit have good toughness and high toughness at low temperatures. Contents : The set includes 3 drill bits with diameters of 3-20 mm. Drill 3-12 mm, steps: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 mm Drill 4-12 mm, steps: 4, 6, 8, 10, 12 mm Drill bit 4 -20 mm, degrees: 4, 6, 8, 10, 12, 14, 16, 18, 20 mm